<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .w{
            width: 800px;
            height: 300px;
            margin: 0 auto;
            background: #a5a5a5;
            
        }
        .fa{
            width: 300px;
            height: 300px;
            background: yellow;
        }
        .s{
            width: 100px;
            height: 30px;
            background: blue;
            position: relative;
        }
        .son{
            width: 200px;
            height: 200px;
            background: green;
            position: absolute;
            top: 30px;
            left: 20;
            display: none;
        }
        .s:hover .son{
            display: block;
        }
    </style>
</head>
<body>
    <div class="w">
        <div class="fa">
            <div class="s">
                <p>dddd</p>
                <div class="son"></div>
            </div>
            
        </div>
    </div>
</body>
</html>